Effects Of Organic Carbon Input On Feeding Behavior Of Soil Bacterivorous Nematode Cephalobidae In Maoershan

Forest soil is the largest organic carbon pool in terrestrial ecosystem.The formation and stability of organic carbon in forest soil mainly depend on the carbon input process of aboveground litter and underground roots.At the same time,the change of soil carbon input will significantly affect the life activities of soil organisms,including soil nematodes and soil microorganisms.Bacterivorous nematode is an important functional group of soil microfood web,and its predation food chain with bacteria is an important component of soil microfood web.In this study,the DNA of bacteria eaten by Cephalobidae in soil was extracted and sequenced with high throughput.The purpose was to identify the groups of bacteria that can be eaten by Cephalobidae under different short-term carbon input conditions,and to explore the changes of Cephalobidae feeding behavior caused by the organic carbon input changes of quality(litter or root)and quantity(with or without litter or root)in growing period,snowing period and freeze-thaw cycle period.The main results are as follows:(1)In the three critical periods,the number and community composition of Cephalobidae′s intestinal bacteria were significantly different from those of bacteria in surrounding soil.The OTUs of Cephalobidae′s intestinal bacteria was significantly less than that of soil bacteria,and Proteobacteria was the dominant phylum.At the genus level,the dominant genera were affected by hydrothermal conditions.Acinetobacter was the dominant genus in the growing period and snow-covered period,while Halomonas and Escherichia were the dominant genus in the freeze-thaw cycle.(2)The amount of short-term carbon input significantly affected the community structure of bacteria fed by Cephalobidae,which varied with the difference of hydrothermal conditions.Except for the non-carbon input treatment during the snow-covered period,the decrease of carbon input during the growing period and the snow-covered period reduced the OTUs number,richness and diversity of the bacterial community fed by Cephalobidae.During the freeze-thaw cycle,reducing the amount of carbon input increased the OTUs number,richness and diversity of the bacterial community fed by Cephalobidae.(3)The source of short-term carbon input also significantly affected the community structure of bacteria fed by Cephalobidae.In the growing period,only root carbon input had a more obvious effect on the community diversity of bacteria fed by Cephalobidae than only litter carbon input,while in the snow-covered period,only litter carbon input had a greater effect.During the snow-covered period,only litter or root carbon input decreased the OTUs number,richness and diversity of the bacterial community fed by Cephalobidae,but simultaneous removal of litter and roots was on the contrary.(4)The correlation between bacteria community of bacteria eaten by Cephalobidae and soil environmental factors was analyzed.During the growing period,soil water content was the most important environmental factor affecting the community composition and diversity of bacteria eaten by Cephalobidae,dissolved organic carbon mainly affected community diversity,ammonium nitrogen and total nitrogen mainly affected community composition.During the snowing period,nitrate nitrogen,dissolved organic carbon and soil microbial biomass nitrogen could significantly affect the composition of bacteria eaten by Cephalobidae.During the freeze-thaw cycle,total nitrogen and total carbon were the most important environmental factors affecting the community composition and diversity of bacteria eaten by Cephalobidae,while water content and dissolved organic carbon mainly affected the community composition.This study clarified the community characteristics of bacteria eaten by Cephalobidae under different hydrothermal conditions and different short-term carbon input,and explored the influencing factors causing the change of feeding behavior of Cephalobidae.It expands our understanding of forest soil nematode-microbial community interaction,and further provides new ideas and supporting data for the further study of temperate forest carbon cycle and soil organisms.